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Checking the sharpness

This topic contains 4 replies, has 5 voices, and was last updated by  tcmeyer 09/18/2019 at 2:58 am.

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    Michael Blakley
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    I am sure there are thousands of ways to check the sharpness of a blade and thousands of arguments about which is best.

    I just have a simple question.  If I am going to use paper cutting as my test.  Should I be using a flimsy paper (like a newpaper or yellowpages paper OR should I be using a piece of copier paper which is thicker than the newspaper?

    My thinking is that the flimsier the paper, the readily it will expose imperfections in the edge.  But I have nothing to back that up other than a hunch.




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    Michael, I use old phone books as a source for testing paper.  They keep dropping them off and I haven’t used a phone book to look up a phone number in many many years.  I don’t think it so much which paper you use as how it feels as the knife slices through the paper, and how it sounds.  It’s only a qualitative test but it gives a basis for comparison between knife edges you’ve sharpened.

    (MarcH's Rack-It)

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    I like the flimsy paper also. I do believe that it reveals more about the quality of the edge than your standard weight printer paper does. It isn’t that hard to get an edge that and push cut printer paper, but getting it to push cut phone book paper is more difficult.

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    <p style=”text-align: left;”>To me, the question is how to check the sharpness while still mounted edge up in the clamp. Very much how how can definitively feel a burr along the entire length by feeling with your finger in an upwards edge trailing direction.</p>
    My favorite thumb nail scrape works great out of the clamp because you can rely on your body for the reference feel. This is cumbersome upside down though. The 3 finger (Josh?) test works but is scary due to slip ups and stitches.

    It begs the question, how do I definitely know when it is time to move to the next grit and  or am done.

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    I believe the “three-finger” method should be attributed to Murray Carter.  Check the youtube video here.

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